Abstract: The effects of nitrogen and potassium on yield and qualities of taro were studied with the design of double saturated D-optimal regression. According to the data obtained, a mathematical model was established; in which N and K applied were independent variables, taro yield and quality were dependent variables. The models analysis showed that taro yield and qualities were influenced largely by nitrogen, potassium and their interaction; and potassium had heavier effect than nitrogen. Within the extent of N 261.75kg/hm2、K2O 757.50kg/hm2, yield increased with the increase of fertilizer, over-rate the yield decreased. The most suitable amounts of fertilizer for over 30000 kg/hm2 yield of taro were N 34.50～531.00(kg/hm2), K2O 526.80～1057.20kg/hm2 under this experimental conditions.